1. Field of the Invention
The invention relates to a key system for electronic musical instruments.
2. Description of Prior Art
In the case of proposed contactless key systems which consist of a contactless control unit and of electronic sound controls, which open (i.e., allow passage of the sound signal) in dependence upon a control voltage or control current there is the disadvantage that although the notes start up softly the time of build-up is the same for all notes.
If, for example, an organ has 30 keyboard stops and 60 keys in the keyboard, then the number of sound controls required between a sound producer and an amplifier of the organ amounts to 1800. If, as is desirable, these sound controls open at different times, then the rate of increase of the control current or of the control voltage must be different. This rate of increase can be controlled by means of an R-C network (with C major) or an R-C network including an impedance transformer (with C minor). Taking into account the number of controls needed, namely 1800, it will be recognized that a key system of this type involves a large amount of equipment which necessitates great spatial requirements and expenditure.
Also, alterations of the time-dependent characteristics of the control voltages in the individual keys would only partially solve this problem, since for example, a trumpet, in relationship to a principal note of equal basic frequency, has a substantially shorter so-called "tone response" (build-up period) than some other instruments.
With regard to this, every musical instrument with mechanically produced notes has a quite definite individual tone response; this term designates the behavior, in time, and according to the frequency, during the build-up period of the note produced. This is in contrast to a resonant circuit which, when excited, begins to oscillate at its resonant frequency, with amplitude constantly increasing from zero until it has reached a relatively steady state having a constant oscillation amplitude. This behavior is normally described with reference to the transient time. In the tone response of an instrument, the sound sets in almost immediately with a substantial amplitude but with a frequency which is at first different from the required frequency. As the amplitude increases the frequency changes to the required frequency. This behavior is designated as "spitting" in the case of wind instruments, e.g., flutes or organs.
The present invention aims to provide a key system which involves relatively low expenditure to build, but enables individual oscillation build-up of each individual note of a register.